I think any martial art can be potentionally self destructive in combat because of ego. Bruce lee was not a great MA because of the system he studied, The man trained 6 hours a day. Ushiba would have never achived his level of mastery without hardwork and training. Granted they could whoop my but any day of the week, but not because of their style, but because of their skill and training.
I doubt a lot of those kids on that fourm has ever been in a "real" fight. I haven't I have used Aikido tech before once or twice, but not in life and death duels. The person who wins in Combat is the person who can control their actions/thoughts/adrenelin the best. Sure MA training may upp the odds, but so does a baseball bat.
Training is a tool for YOUR self improvement and hopefully improve yourself to the point you dont need to get angery and fight or do something stupid to get into a fight. Remember dont judge anybody, Ushiba's students say that Ushiba never classified people in catagories of, "that guy is bad I wont help him, or that guy is good I will hang out with him." Ushiba had a lot of compassion for human kind, that is why he created Aikido.